The subject of the invention is a process of transmission in a communication network in which at least certain connections are of xe2x80x9cwirelessxe2x80x9d type. The invention applies in particular in the field of domestic communication networks.
In a domestic communication network, several types of multimedia equipment can coexist. Some of these equipment items may be linked together by way of cables. They then constitute a cabled group. A domestic communication network can comprise several cabled groups. A domestic communication network comprising several cabled groups can also comprise wireless links. These wireless links are intended to link the cabled groups to one another. The number of wireless links must be sufficient for each cabled group to be linked to at least one other cabled group.
The communication by wireless link can be effected simply via a link between two items of equipment in so-called xe2x80x9cpoint-to-pointxe2x80x9d mode. However, more generally, there may be several simultaneous point-to-point links in the same domestic network. More generally still, these wireless links may together constitute what is referred to as a bridge in network terminology, that is to say a set of xe2x80x9cmultipoint-multipointxe2x80x9d links allowing the interconnecting of cabled buses of the IEEE1394-1995 type.
The set of wireless links constitutes the domestic wireless communication network. The cabled groups of the domestic communication network constitute the elements of the domestic wireless communication network.
For reasons of propagation in a domestic environment, it is possible that certain wireless links between various elements of the domestic wireless communication network may not be established. Consequently, within the domestic wireless communication network, it may happen that certain elements are not linked to all the others. Such a network is said to have incomplete connectivity.
The available passband is a limited resource and must be used in the most effective manner possible. The expression effective use of frequency is understood to mean any frequency allocation scheme which minimizes in particular the transmission of service data, such as for example data serving for the coordination of the members (devices) of the network.
The purpose of the invention is to propose an effective wireless channel access process.
The subject of the invention is a process of transmission in a transmission network comprising devices connected to the network, at least certain devices being linked by at least one wireless link, characterized in that:
the wireless communications are performed according to an isochronous TDMA type protocol, in which a frame is divided into time windows allocated on reservation to devices,
the allocation of a window of a frame to a device being such that any device can deduce it from the number of windows reserved per frame by each device and from at least one other parameter which identifies the device which made the request.
The allocating of the windows of a frame is performed according to a nonequivocal method known by each device of the network, which may thus ascertain this allocation with the aid of a minimum of parameters.
According to a particular embodiment, each frame comprises one control window per device linked to the wireless part of the network, the position and order of the control windows within each frame being known by all the devices of this Wireless part of the network.
According to a particular embodiment, the control windows are distributed within the frame and the positions of these windows are identical at each frame.
According to a particular embodiment, the position of the control windows within a frame is determined subsequent to a reinitialization of the network, for example subsequent to the connecting or to the disconnecting of a device of the network.
A change of topology induces a modification of the allocation of the windows within a frame. This item of information must consequently also be broadcast.
According to a particular embodiment, when registering a device in the network, an order number is allocated to it, the order of the control windows being deduced from the order of the numbers allocated to the devices of the network. In the embodiment of the invention, this number is the xe2x80x9cphysical addressxe2x80x9d of a device.
According to a particular embodiment, the control window of a device comprises as appropriate a windows reservation data packet.
According to a particular embodiment, a device receiving a data packet relating to a reservation includes it in its next control window.
The reservation information is thus propagated gradually to all the devices of the network.
According to a particular embodiment, on each change of topology of the network, each device transmits a signalling of echo type in its control window, the said signalling intended to be broadcast in the network and to be returned by each of the other devices, the device which sent the signalling determining on the basis of the returns of signalling by the other devices the duration of broadcasting of its request for reservation in the network.
The expression change of topology of the network is understood to mean the connecting or the disconnecting of a device connected to the wireless part of the network. By virtue of the above method, a device is aware of the time required for one of its frames to reach all the devices of the network.
According to a particular embodiment, a device having sent a windows reservation request implements this reservation only after a duration corresponding to the duration of broadcasting of its control data in the network.
According to a particular embodiment, a frame furthermore comprises a time interval whose use is governed by a contentious process reserved for asynchronous transmission.